1. Field of the Invention
The invention relates to a lock device, more particularly to a lock device which is capable of activating an electrical anti-theft system.
2. Description of the Related Art
Referring to FIG. 1, a conventional vehicle door lock is shown to comprise a lock shell 90, a key plug 91, an anti-dusting cover assembly 92 and an annular retaining cap 93. The lock shell 90 is an elongated hollow member which confines a through-hole 900 for receiving the key plug 91 therein. The lock shell 90 has an inner wall surface which is formed with an axially extending retaining groove 901. The key plug 91 has a recessed front end 911 with an end wall that is formed with a keyhole 912. Tumbler members (not shown) extend into the keyhole 912 and are connected to an axially extending retaining unit 913 which projects from an external wall surface of the key plug 91. The front end 911 has two inner side walls which are formed with a respective spring-receiving groove 914 for receiving a spring 915 therein. The anti-dusting cover assembly 92 is secured on the key plug 91 by means of the annular retaining cap 93 and includes a cover plate 921 which is formed with a key slot 920 and which has two sides that are respectively provided with two rearwardly extending pivot ears 922. A pivot pin 924 extends between the pivot ears 922 and has two ends which extend into a pivot hole 923 that is formed in a respective one of the pivot ears 922. The cover assembly 92 further includes an anti-dusting plate 925 which has two sides that are mounted pivotally on the pivot pin 924. The anti-dusting plate 925 is used to cover the key slot 920 of the cover plate 921 and is biased so as to abut normally against the cover plate 921 by means of a torsion spring 926 which is disposed around the pivot pin 924. The annular retaining cap 93 is provided on the front end of the lock shell 90 and is formed with a through-hole 931. The springs 915 bias the cover plate 921 toward the annular retaining cap 93 in order to prevent the entry of dust via the through-hole 931 of the latter.
When a key 94 is inserted into the key slot 920 of the cover plate 921 so as to unlock the door lock, the key 94 pushes the anti-dusting plate 925 to pivot rearwardly against the action of the torsion spring 926. When the key 94 extends into the keyhole 912, the key bits 941 of the key 94 activate the tumbler members in order to permit disengagement of the retaining unit 913 from the retaining groove 901, thereby permitting the rotation of the key plug 91 relative to the lock shell 90 to unlock the door lock.
The above procedure for unlocking the conventional door lock is usually accomplished within one to two seconds. The length of time required to pick the conventional door lock with the use of a screw driver, a universal key or a similar article, however, ranges from a few seconds to a few minutes, depending upon the skill of the thief.
Note that the conventional electrical anti-theft systems installed in most vehicles are activated only after one of the doors of a vehicle is opened or after the vehicle is moved. Accordingly, there is thus a need to provide a lock device which is capable of activating a conventional electrical anti-theft system before the door of a vehicle can be opened when the lock device is being picked.